#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <algorithm>
#include <math.h>

using namespace std;

long long dp[25][25];

int main() {
    int x, y, n, m;
    cin >> n >> m >> x >> y;

    dp[0][1] = 1;
    x += 1; y += 1;

    for (int i = 1; i <= n + 1; i++)
    {
        for (int j = 1; j <= m + 1; j++)
        {
            if (i != x && j != y && abs(i - x) + abs(j - y) == 3)
                dp[i][j] = 0;
            else if (i == x && j == y)
                dp[i][j] = 0;
            else
                dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
        }
    }

    cout << dp[n + 1][m + 1] << endl;
    return 0;
}